Combustor and gas turbine

ABSTRACT

There is provided a combustor including a nozzle main body ( 16 ) that includes a shaft body ( 24 ) which extends along an axis and has, inside the shaft body ( 24 ), a purge air flow path ( 29 ), which extends along the axis to a tip portion of the shaft body ( 24 ) and into which compressed air is introduced, and an air spraying hole ( 39 ), which is formed in the tip portion of the shaft body ( 24 ) and connects the purge air flow path ( 29 ) to an outer surface of the shaft body ( 24 ), a swirling blade ( 26 ), which overhangs from an outer circumferential surface of the shaft body ( 24 ) in a diameter direction of the axis and swirls a fluid flowing to a downstream side of an axial direction around the axis, and a fuel spraying hole ( 38 ), and a sealing member ( 40 ) that seals the air spraying hole ( 39 ) and is formed of a metal having a melting point lower than a melting point of a metal forming the nozzle main body ( 16 ).

TECHNICAL FIELD

The present invention relates to a combustor and a gas turbine. Priorityis claimed on Japanese Patent Application No. 2016-067125, filed on Mar.30, 2016, the content of which is incorporated herein by reference.

BACKGROUND ART

In general, a gas turbine includes a compressor that compresses externalair to generate compressed air, a combustor that combusts fuel in thecompressed air to generate a high-temperature and high-pressurecombustion gas, and a turbine that is rotation-driven by the combustiongas.

Although a rise in the temperature of a turbine inlet is necessary toimprove the efficiency of the gas turbine, there is a problem of anexponential increase in NOx accompanying the temperature rise. Forexample, a combustor disclosed in the following PTL 1 includes, as acountermeasure against an increase in NOx, a burner that forms anair-fuel mixture by a swirling flow to suppress the formation of alocally high temperature region.

The burner of the combustor includes a nozzle which is a shaft bodyextending along a burner axis, a burner cylinder which surrounds anouter circumference of the nozzle and jets compressed air and fuel to adownstream side, and a swirling blade which swirls a fluid in the burnercylinder around a burner axis.

CITATION LIST Patent Literature

PTL 1 Japanese Unexamined Patent Application, First Publication No.2006-336996

SUMMARY OF INVENTION Technical Problem

It is known that a phenomenon, in which a flame moves upstream (vortexcore flashback) of a swirling flow when a swirling premixed gascombusts, often occurs. When an abnormal fuel such as a vortex coreflashback occurs, there is a possibility that flame sticks to the nozzleand damage due to heat occurs. Therefore, it is desirable to suppressthis occurrence.

The invention provides a combustor and a gas turbine capable of avoidinga vortex core flashback even in a case where abnormal combustion such asthe vortex core flashback has occurred.

Solution to Problem

According to a first aspect of the invention, there is provided acombustor including a nozzle main body that includes a shaft body whichextends along an axis and has, inside the shaft body, a purge air flowpath, which extends along the axis to a tip portion of the shaft bodyand into which compressed air is introduced, and an air spraying hole,which is formed in the tip portion of the shaft body and connects thepurge air flow path to an outer surface of the shaft body, a swirlingblade, which overhangs from an outer circumferential surface of theshaft body in a diameter direction of the axis and swirls a fluidflowing to a downstream side of an axial direction around the axis, anda fuel spraying hole, and a sealing member that seals the air sprayinghole and is formed of a metal having a melting point lower than amelting point of a metal forming the nozzle main body.

In such a configuration, even in a case where abnormal combustion suchas a vortex core flashback has occurred, it is possible to avoid thevortex core flashback by compressed air being sprayed from the airspraying hole onto the downstream side of the nozzle main body.Accordingly, it is possible to prevent the combustor from being damagedby heat due to a vortex core flashback.

In the combustor, the sealing member may have a plate shape, may beformed around an opening of the air spraying hole on an outer surfaceside of the shaft body, and may be joined to a recessed portion intowhich the sealing member can be fitted.

In such a configuration, the thickness of a sealing member can bechanged according to conditions of use or specifications of the gasturbine. That is, it is easy to make the sealing member reliably meltwhen a vortex core flashback occurs.

According to a second aspect of the invention, there is provided acombustor including a nozzle main body that includes a shaft body whichextends along an axis and has, inside the shaft body, a purge air flowpath, which extends along the axis and into which compressed air isintroduced, and an internal space, which is formed in a tip portion ofthe shaft body and communicates with the purge air flow path, a swirlingblade, which overhangs from an outer circumferential surface of theshaft body in a diameter direction of the axis and swirls a fluidflowing to a downstream side of an axial direction around the axis, anda fuel spraying hole. The tip portion of the shaft body has a thinportion in which a thickness between an outer surface of the shaft bodyand an inner surface of the internal space is smaller than a thicknessof the other part of the shaft body.

In such a configuration, even in a case where abnormal combustion suchas a vortex core flashback has occurred, it is possible to avoid thevortex core flashback by the thin portion melting and compressed airbeing sprayed onto the downstream side of the nozzle main body.

In addition, the thickness of the tip portion can be changed accordingto conditions of use or specifications of the gas turbine. That is, itis easy to make the tip portion reliably melt when a vortex coreflashback occurs.

According to a third aspect of the invention, there is provided acombustor including a nozzle main body that includes a shaft body whichextends along an axis and has, inside the shaft body, a purge air flowpath, which extends along the axis and into which compressed air isintroduced, an internal space, which is formed in a tip portion of theshaft body and communicates with the purge air flow path, and an airspraying hole, which is formed in the tip portion of the shaft body andconnects the internal space to an outer surface of the shaft body, aswirling blade, which overhangs from an outer circumferential surface ofthe shaft body in a diameter direction of the axis and swirls a fluidflowing to a downstream side of an axial direction around the axis, anda fuel spraying hole, and a valve device which is provided inside theinternal space, opens and closes the air spraying hole, and has a valveshaft which is held so as to freely advance and retreat in onedirection, a valve body which is attached to a tip of the valve shaftand is movable to a first position of being in close contact with theair spraying hole and a second position of being separated away from theair spraying hole, a biasing member which biases the valve body in adirection of the first position, and a thermal elongation member whichis disposed between the valve body and the air spraying hole, is formedof a metal having a coefficient of thermal expansion higher than acoefficient of thermal expansion of a metal forming the biasing member,and moves the valve body to the second position by thermal elongation.

In such a configuration, even in a case where abnormal combustion suchas a vortex core flashback has occurred, it is possible to avoid thevortex core flashback by compressed air being sprayed from the airspraying hole onto the downstream side of the nozzle main body.Accordingly, it is possible to prevent the combustor from being damagedby heat due to a vortex core flashback.

In addition, the valve device can be repeatedly used even after thenozzle main body has exposed to the vortex core flashback.

According to a fourth aspect of the invention, there is provided a gasturbine including the combustor, a compressor that compresses air andsupplies the air to the combustor, and a turbine that is driven by acombustion gas formed by combustion of fuel in the combustor.

Advantageous Effects of Invention

According to the invention, even in a case where abnormal combustionsuch as a vortex core flashback has occurred, it is possible to avoidthe vortex core flashback by compressed air being sprayed onto thedownstream side of the nozzle main body.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating a configuration of a gas turbineaccording to a first embodiment of the invention.

FIG. 2 is a sectional view of a vicinity of a combustor of the gasturbine according to the first embodiment of the invention.

FIG. 3 is a sectional view of the combustor according to the firstembodiment of the invention.

FIG. 4 is a sectional view of a main burner according to the firstembodiment of the invention.

FIG. 5 is a sectional view taken along an arrow V of FIG. 4 and is aview for describing disposition of an air spraying hole according to thefirst embodiment of the invention.

FIG. 6 is a view for describing a shape of an air spraying holeaccording to a first modification example of the first embodiment of theinvention.

FIG. 7 is a view for describing a shape of an air spraying holeaccording to a second modification example of the first embodiment ofthe invention.

FIG. 8 is a sectional view of a main nozzle according to a secondembodiment of the invention.

FIG. 9 is a sectional view of a main nozzle according to a thirdembodiment of the invention.

FIG. 10 is a sectional view of a main nozzle according to a fourthembodiment of the invention.

FIG. 11 is a sectional view of the main nozzle according to the fourthembodiment of the invention and is a view illustrating a valve device inan open state.

DESCRIPTION OF EMBODIMENTS First Embodiment

Hereinafter, a gas turbine 1 according to a first embodiment of theinvention will be described in detail with reference to the drawings.

As illustrated in FIG. 1, the gas turbine 1 of the embodiment includes acompressor 2 that compresses air A to generate compressed air, aplurality of combustors 3 that combust fuel F in the compressed air togenerate a high-temperature and high-pressure combustion gas, and aturbine 4 that is rotation-driven by the combustion gas.

The compressor 2 has a compressor rotor 6 that rotates about arotational axis Ar and a compressor casing 7 that rotatably covers thecompressor rotor 6. The turbine 4 has a turbine rotor 8 that rotatesabout the rotational axis Ar and a turbine casing 9 that rotatablycovers the turbine rotor 8.

The rotational axis of the compressor rotor 6 and the rotational axis ofthe turbine rotor 8 are located on the same straight line. Thecompressor rotor 6 and the turbine rotor 8 are connected to each otherand form a gas turbine rotor 10. The compressor casing 7 and the turbinecasing 9 are connected to each other and form a gas turbine casing 11.

For example, a rotor of a generator GEN is connected to the gas turbinerotor 10. The combustors 3 are fixed to the gas turbine casing 11.

As illustrated in FIG. 2, each of the combustors 3 has a combustioncylinder 13 (or a transition piece) and a fuel jetter 14. The fuel Fcombusts inside the combustion cylinder 13. The combustion cylinder 13sends a combustion gas, which is generated as a result of combustion ofthe fuel F, to the turbine 4. The fuel jetter 14 jets the fuel F and thecompressed air A into the combustion cylinder 13.

As illustrated in FIG. 3, the fuel jetter 14 includes a pilot burner 15,main burners 16 (nozzle main bodies), and a burner holding cylinder 17.The pilot burner 15 diffuses and combusts the jetted fuel. The mainburners 16 premix and combust the jetted fuel. The burner holdingcylinder 17 holds the pilot burner 15 and the main burners 16.

The pilot burner 15 has a pilot nozzle 19, a pilot burner cylinder 18,and a plurality of swirling blades 20. The pilot nozzle 19 is a shaftbody about a combustor axis Ac, which extends in an axial direction Da.The pilot burner cylinder 18 covers an outer circumference of the pilotnozzle 19. The swirling blades 20 swirl the compressed air A around thecombustor axis Ac. Herein, one side of the axial direction Da, which isa direction where the combustor axis Ac extends, is set as an upstreamside (the right in FIG. 3), and the other side is set as a downstreamside (the left in FIG. 3). In addition, the combustor axis Ac is also aburner axis of the pilot burner 15.

A spraying hole is formed in a downstream end portion of the pilotnozzle 19. The plurality of swirling blades 20 are provided on theupstream side of a position at which the spraying hole is formed. Eachof the swirling blades 20 extends from the outer circumference of thepilot nozzle 19 in a direction including a radial direction componentand is connected to an inner circumferential surface of the pilot burnercylinder 18.

The pilot burner cylinder 18 has a main body 21 located on the outercircumference of the pilot nozzle 19 and a cone portion 22, which isconnected to a downstream side of the main body 21 and has a diametergradually increasing toward the downstream side. The plurality ofswirling blades 20 are connected to an inner circumferential surface ofthe main body 21 of the pilot burner cylinder 18. The compressed air A,which is obtained by air being compressed by the compressor 2 from theupstream side of the pilot burner cylinder, flows into the pilot burnercylinder 18. The pilot burner cylinder 18 jets, from a downstream endthereof, fuel sprayed from the pilot nozzle 19, along with thecompressed air A. This fuel diffuses and combusts in the combustioncylinder 13.

The plurality of main burners 16 are disposed so as to be arranged in acircumferential direction about the combustor axis Ac such that an outercircumferential side of the pilot burner 15 is surrounded.

Each of the main burners 16 has a main nozzle 24, a main burner cylinder25, and a plurality of swirling blades 26. The main nozzle 24 is a shaftbody extending along a burner axis Ab that is parallel to the combustoraxis Ac. The main burner cylinder 25 covers an outer circumference ofthe main nozzle 24. The swirling blades 26 swirl the compressed air Aaround the burner axis Ab.

Since the burner axis Ab of each of the main burners 16 is parallel tothe combustor axis Ac, an axial direction related to the combustor axisAc and an axial direction related to the burner axis Ab are the samedirection.

In addition, the upstream side of the axial direction related to thecombustor axis Ac is the upstream side of the axial direction related tothe burner axis Ab. The downstream side of the axial direction relatedto the combustor axis Ac is the downstream side of the axial directionrelated to the burner axis Ab.

The main nozzle 24 is formed of, for example, a metal such as stainlesssteel. A metal having a melting point of 1,000° C. or higher can beadopted as a metal for forming the main nozzle 24.

The plurality of swirling blades 26 are provided at an intermediateportion of the main nozzle 24 in the axial direction Da. The main burnercylinder 25 has a main body 27 which is located on an outercircumference of the main nozzle 24 and an extended portion 28, which isconnected to the downstream side of the main body 27 and extends towardthe downstream side.

The plurality of swirling blades 26 are connected to an innercircumferential surface of the main body 27 of the main burner cylinder25. A plurality of fuel spraying holes 38 (refer to FIG. 4) for sprayingfuel (gas fuel) are formed in each of the plurality of swirling blades26. Fuel is supplied into the main nozzle 24 and the fuel is suppliedfrom the main nozzle 24 to the swirling blades 26.

The compressed air A, which is obtained by air being compressed by thecompressor 2 from the upstream side of the main burner cylinder, flowsinto the main burner cylinder 25. The compressed air A and fuel sprayedfrom the swirling blades 26 are mixed to form a premixed gas PM in themain burner cylinder 25. The main burner cylinder 25 jets the premixedgas PM from a downstream end thereof. The fuel in the premixed gas PM ispremixed and combusts in the combustion cylinder 13.

The burner holding cylinder 17 has a cylindrical shape about thecombustor axis Ac, and covers an outer circumferential side of theplurality of main burner cylinders 25.

The combustion cylinder 13 has a combusting unit 31 and a combustion gasguiding unit 32. The combusting unit 31 has a cylindrical shape aboutthe combustor axis Ac. The combusting unit 31 forms a combustion region30 where fuel jetted from the main burners 16 and the pilot burner 15combusts. The combustion gas guiding unit 32 has a tubular shape. Thecombustion gas guiding unit 32 leads a combustion gas generated by thecombustion of fuel into a combustion gas flow path of the turbine 4. Thecombustion gas guiding unit 32 of the combustion cylinder 13 is formedon the downstream side of the combusting unit 31 of the combustioncylinder 13.

As illustrated in FIG. 4, each of the swirling blades 26 of the mainburner 16 overhangs from an outer circumferential surface of the mainnozzle 24 in a diameter direction and is connected to an innercircumferential surface of the main burner cylinder 25. The swirlingblades 26 are formed to swirl a fluid circulating on the downstream sidearound the burner axis Ab.

The main nozzle 24 has a main nozzle main body 34 having a cylindricalshape and a sharp tip portion 35 provided on the downstream side of themain nozzle main body 34. The tip portion 35 gradually becomes thinnertoward the downstream side. In other words, the tip portion 35 is formedin a tapered shape tapering off toward a tip on the downstream side.

Each of the swirling blades 26 has a nozzle-side connecting portion 45,a cylinder-side connecting portion 46, and a profile portion 36. Thenozzle-side connecting portion 45 is connected to an outercircumferential surface of the main nozzle main body 34. Thecylinder-side connecting portion 46 is connected to the innercircumferential surface of the main burner cylinder 25. A smooth andcontinuous profile surface 37 is formed in the profile portion 36 inorder to swirl a fluid which has flowed from the upstream side aroundthe burner axis Ab. A circumferential direction about the burner axis Abwill be hereinafter simply referred to as a circumferential directionDc, and a diameter direction Dr about the burner axis Ab will behereinafter simply referred to as the diameter direction Dr.

The plurality of fuel spraying holes 38 for spraying the fuel F areformed in each of the swirling blades 26.

Each of the main burners 16 has fuel flow paths 41, a purge air flowpath 29, air spraying holes 39, and sealing members 40. The fuel flowpaths 41 spray the fuel F from the fuel spraying holes of the swirlingblades 26. Inside the main nozzle 24, the purge air flow path 29 extendsto the tip portion 35 of the main nozzle 24 along the burner axis Ab,and the compressed air A is introduced into the purge air flow path. Thecompressed air A is sprayed through the air spraying holes 39. Thesealing members 40 seal the air spraying holes 39.

The purge air flow path 29 has an air flow path main body 29 a and adiameter increasing portion 29 b. The air flow path main body 29 aextends along the burner axis Ab inside the main nozzle 24. The diameterincreasing portion 29 b is formed inside the tip portion 35 of the mainnozzle 24, which is on the downstream side of the air flow path mainbody 29 a.

The compressed air A generated by the compressor (refer to FIG. 1) isintroduced in the purge air flow path 29. The purge air flow path 29extends to the vicinity of an outer surface of the tip portion 35 of themain nozzle 24. A sectional shape of the diameter increasing portion 29b seen in the axial direction Da is larger than a sectional shape of theair flow path main body 29 a seen in the axial direction Da. It ispreferable that the diameter increasing portion 29 b have a shapefollowing the outer surface of the tip portion 35 of the main nozzle 24.

The air spraying holes 39 are formed in the tip portion 35 of the mainnozzle 24. Each of the air spraying holes 39 connects the diameterincreasing portion 29 b of the purge air flow path 29 to the outersurface of the tip portion 35 of the main nozzle 24. As illustrated inFIG. 5, three air spraying holes 39 are equidistantly formed in acircumferential direction of the burner axis Ab. The number of the airspraying holes 39 is not limited thereto.

An axis of each of the air spraying holes 39 is tilted toward thedownstream side as approaching from a burner axis Ab side to an outsidein the diameter direction. Each of the air spraying holes 39 is orientedsuch that the compressed air A introduced in the air spraying hole 39via the purge air flow path 29 is sprayed toward the downstream side ofthe main nozzle 24. A sectional shape of each of the air spraying holes39 of the embodiment is circular.

Each of the sealing members 40 is a member that closes each of the airspraying holes 39. A surface of each of the sealing members 40, whichfaces the outside in the diameter direction, is formed to be flush withthe outer surface of the tip portion 35 of the main nozzle 24. Thesealing members 40 of the embodiment are formed of aluminum (Al). Thesealing members 40 of the embodiment are buried in the air sprayingholes 39 by melting an aluminum brazing material.

Without being limited thereto, a low melting point metal having amelting point of 500° C. to 600° C., the melting point being lower thanthat of the metal forming the main nozzle 24, can be used as a materialfor forming the sealing members 40.

Next, an operation and an effect of the gas turbine 1 of the embodimentwill be described.

The compressor 2 sucks external air and compresses the air. The aircompressed by the compressor 2 is guided into the main burners 16 andthe pilot burner 15 of each of the combustors 3. Fuel is supplied from afuel supply source to the main burners 16 and the pilot burner 15. Themain burners 16 jet the premixed gas PM, which is obtained by premixingfuel and air, into the combusting unit 31 of the combustion cylinder 13.The premixed gas PM is premixed and combusts in the combusting unit 31.In addition, the pilot burner 15 jets each of fuel and air into thecombusting unit 31 of the combustion cylinder 13. This fuel diffuses andcombusts or is premixed and combusts in the combusting unit 31. Thecombustion mode can be changed in any manner by selecting a fuel jettingpart of the pilot burner 15. A high-temperature and high-pressurecombustion gas generated by the combustion of fuel in the combustingunit 31 of the combustion cylinder 13 is led into the combustion gasflow path of the turbine 4 by the combustion gas guiding unit 32 of thecombustion cylinder 13 to rotate the turbine rotor 8.

Air compressed by the compressor 2 is introduced from an upstream end ofthe main burner cylinder 25 into the main burner cylinder 25. This airswirls around the burner axis Ab by the plurality of swirling blades 26in the main burner cylinder 25. Fuel is sprayed from the fuel sprayingholes 38 of the plurality of swirling blades 26 into the main burnercylinder 25.

After the fuel F sprayed from the swirling blades 26 and the air Aflowing to the downstream side while swirling are premixed in the mainburner cylinder 25, the fuel and the air are jetted, as the premixed gasPM, from the downstream end of the main burner cylinder 25 into thecombustion cylinder 13.

A swirling flow formed by the plurality of swirling blades 26 promotesmixing of the fuel F, which is sprayed from the fuel spraying holes 38of the plurality of swirling blades 26 in the main burner cylinder 25,and the air A. In addition, a flame stabilizing effect of premixed flameformed by the combustion of the premixed gas PM is enhanced by thepremixed gas PM being jetted from the main burner cylinder 25 into thecombustion cylinder 13 while swirling.

For example, when the swirling premixed gas PM combusts, flame movesupstream in some cases due to a vortex core flashback. When the vortexcore flashback, which is flame at 700° C. or higher, reaches the mainnozzle 24, the sealing members 40 formed of aluminum having a meltingpoint lower than that of the metal forming the main nozzle 24 melt.

Accordingly, the compressed air A is sprayed from the air spraying holes39 as purge air. By the compressed air A being sprayed, the vortex coreflashback returns to the downstream side.

According to the embodiment, even in a case where abnormal combustionsuch as a vortex core flashback has occurred, the compressed air A fromthe air spraying holes 39 is sprayed onto the downstream side of themain nozzle 24. For this reason, it is possible to avoid a vortex coreflashback by lowering the distribution of fuel concentration of a vortexcore. Accordingly, it is possible to prevent the combustors from beingdamaged by heat due to a vortex core flashback.

Although the sectional shape of each of the air spraying holes 39 iscircular in the embodiment, the sectional shape is not limited thereto.For example, as air spraying holes 39B according to a first modificationexample illustrated in FIG. 6, the sectional shape may be a slit in thecircumferential direction of the burner axis Ab. In addition, one airspraying hole 39C may be formed along the burner axis Ab as in a secondmodification example illustrated in FIG. 7.

In the embodiment, the fuel spraying holes 38 for spraying the fuel Fare formed in each of the swirling blades 26, and the fuel F is sprayedinto the main burner cylinder 25 from the fuel spraying holes. However,a member in which a separate fuel spraying hole is formed may beprovided instead of forming the fuel spraying holes 38 in each of theswirling blades 26.

Second Embodiment

Hereinafter, a combustor of a second embodiment of the invention will bedescribed in detail with reference to the drawings. Differences from thefirst embodiment described above will be mainly described anddescription of the same portions will be omitted in the embodiment.

As illustrated in FIG. 8, each of air spraying holes 39D of theembodiment has a spraying hole main body 43 and a plate accommodatingportion 44 formed on an outer surface side of the main nozzle 24.

Sealing members 40D of the embodiment are metal plates having a plateshape.

The plate accommodating portion 44 is a recessed portion, which isformed around an opening of each of the air spraying holes 39D on anouter surface 24 a side of the main nozzle 24 and into which each of thesealing members 40D can be fitted.

The plate accommodating portion 44 is formed so as to be larger than asectional shape of the spraying hole main body 43. The plateaccommodating portion 44 has a shape corresponding to each of thesealing members 40D, which is a metal plate. The plate accommodatingportion 44 is formed such that a surface of each of the sealing members40D and the outer surface of the main nozzle 24 are disposed on thesubstantially same plane when each of the sealing members 40D is fittedin the plate accommodating portion 44.

Each of the sealing members 40D, which is a metal plate, has apredetermined thickness. A planar shape of each of the sealing members40D may be circular, or may be rectangular. After being fitted in theplate accommodating portion 44, each of the sealing members 40D isjoined to the plate accommodating portion 44 by welding or the like.

The sealing members 40D are formed of an aluminum alloy. Without beinglimited thereto, a low melting point metal having a melting point of500° C. to 600° C., the melting point being lower than that of the metalforming the main nozzle 24, can be used as a material for forming thesealing members 40D.

The thickness of each of the sealing members 40D is set as appropriateby experiments or the like. The thickness of each of the sealing members40D is set to a thickness, which allows reliable melting when exposed toflame such as a vortex core flashback and does not allow melting duringnormal operation of the gas turbine. That is, the thickness of each ofthe sealing members 40D can be regulated according to conditions of use.The depth of the plate accommodating portion 44 is set as appropriateaccording to the thickness of each of the sealing members 40D.

According to the embodiment, the thickness of each of the sealingmembers 40D can be changed according to conditions of use orspecifications of the gas turbine. That is, it is easy to make thesealing members reliably melt when a vortex core flashback occurs.

Third Embodiment

Hereinafter, a combustor of the second embodiment of the invention willbe described in detail with reference to the drawings. Differences fromthe first embodiment described above will be mainly described anddescription of the same portions will be omitted in the embodiment.

As illustrated in FIG. 9, the main nozzle 24 of the embodiment has thecylindrical main nozzle main body 34 and a tip portion 35E, of which atip side is formed by a thin plate and which has an internal space 47.The tip portion 35E and the main nozzle main body 34 can be joined toeach other, for example, by welding.

The internal space 47 of the tip portion 35E communicates with the purgeair flow path 29.

The tip side of the tip portion 35E is formed to have a thickness T of,for example, 2 mm or less. In other words, the tip portion 35E has athin portion 48 in which the thickness T between an outer surface 24 aof the main nozzle 24 and an inner surface 47 a of the internal space 47is smaller than those of other parts of the main nozzle 24.

A range in which the tip portion 35E is formed so as to have thethickness T of 2 mm or less is set as appropriate by experiments or thelike. In the range in which the tip portion 35E is formed so as to havethe thickness T of 2 mm or less, it is preferable to set a thickness,which allows reliable melting when exposed to flame such as a vortexcore flashback and does not allow melting during normal operation of thegas turbine. The thickness T of the tip portion 35E can be regulatedaccording to conditions of use.

For example, when flame moves upstream due to a vortex core flashbackand reaches the main nozzle 24, the thin portion 48 of the tip portion35E, which is formed to be thinner than other parts of the main nozzle24, melts.

Accordingly, the compressed air A is sprayed as purge air. By thecompressed air A being sprayed, the vortex core flashback returns to thedownstream side.

According to the embodiment, even in a case where abnormal combustionsuch as a vortex core flashback has occurred, the thin portion 48 meltsand the compressed air A is sprayed onto the downstream side of the mainnozzle 24. Accordingly, it is possible to avoid a vortex core flashbackby lowering the distribution of fuel concentration of a vortex core.

In addition, the thickness T of the tip portion 35E can be changedaccording to conditions of use or specifications of the gas turbine.That is, it is easy to make the tip portion 35E reliably melt when avortex core flashback occurs.

Fourth Embodiment

Hereinafter, a combustor of a fourth embodiment of the invention will bedescribed in detail with reference to the drawings. Differences from thefirst embodiment described above will be mainly described anddescription of the same portions will be omitted in the embodiment.

As illustrated in FIG. 10, a tip portion 35F of a main nozzle 24 of theembodiment has a cylindrical internal space 47F, an air spraying hole39F, and a valve device 49. The internal space 47F is formed so as toextend along the burner axis Ab. The air spraying hole 39F connects theinternal space 47F to the outer surface 24 a of the main nozzle 24. Thevalve device 49 is provided in the internal space 47F and opens andcloses the air spraying hole 39F.

The valve device 49 has a valve shaft 50, a valve body 51, a firstcompression coil spring 53, and a second compression coil spring 54(thermal elongation member). The valve shaft 50 extends along the burneraxis Ab. The valve body 51 is provided on a tip of the valve shaft 50.The first compression coil spring 53 is provided on the upstream side ofthe valve body 51. The second compression coil spring 54 is provided onthe downstream side of the valve body 51.

The valve shaft 50 is held by a cylindrical holding member 55 so as tofreely advance and retreat in the axial direction Da. The holding member55 is supported by a supporting member 56 provided on the upstream sideof the internal space 47F. The supporting member 56 is configured by aplurality of bar-like members that connects an outer surface of theholding member 55 to an inner surface of the internal space 47F.

The valve body 51 closes down an opening 57 of the air spraying hole 39Fon an internal space 47F side by the valve shaft 50 moving to thedownstream side. That is, the opening 57 of the air spraying hole 39F onthe internal space 47F side functions as a valve seat corresponding tothe valve body 51. The valve body 51 is movable to a first position ofbeing in close contact with an air spraying hole 38F, which isillustrated in FIG. 10, and a second position of being separated awayfrom the air spraying hole 38F, which is illustrated FIG. 11.

The first compression coil spring 53 is a biasing member that biases thevalve body 51 in a direction of the first position. The firstcompression coil spring 53 is disposed between a surface 51 a of thevalve body 51, which faces the upstream side, and the supporting member56. The valve shaft 50 is inserted on an inner circumferential side ofthe first compression coil spring 53 in the diameter direction. That is,the valve shaft 50 functions as a guide of the first compression coilspring 53.

One seat of the first compression coil spring 53 abuts a back surface ofthe valve body 51, and the other seat of the first compression coilspring 53 abuts the supporting member 56. Accordingly, elastic energy ofthe first compression coil spring 53 is exerted such that the valve body51 is moved to the downstream side.

The second compression coil spring 54 is disposed between a surface 51 bof the valve body 51, which faces the downstream side, and a surface 47b of the internal space 47F, which faces the upstream side. One seat ofthe second compression coil spring 54 abuts a fringe of the opening 57of the air spraying hole 38F on the internal space 47F side, and theother seat of the second compression coil spring 54 abuts the surface 51b of the valve body 51, which faces the downstream side. Accordingly,elastic energy of the second compression coil spring 54 is exerted suchthat the valve body 51 is moved to the downstream side.

A shaft 58 that functions as a guide of the second compression coilspring 54 is provided on a tip of the valve body 51.

Spring constants of the first compression coil spring 53 and the secondcompression coil spring 54 are selected such that the valve body 51closes the air spraying hole 38F in an atmosphere of a temperature (forexample, 450° C.) of the compressed air A during normal operation of thegas turbine. In addition, by the pressure of the compressed air A beingexerted on the surface 51 a of the valve body 51, which faces theupstream side, the air spraying hole 38F is closed during normaloperation of the gas turbine. That is, the compressed air A supplied tothe internal space 47F via the purge air flow path 29 is not sprayedfrom the air spraying hole 38F during normal operation of the gasturbine.

The coefficient of thermal expansion of a metal forming the secondcompression coil spring 54 is higher than the coefficient of thermalexpansion of a metal forming the first compression coil spring 53. Thatis, the second compression coil spring 54 expands more than the firstcompression coil spring 53 does in response to a temperature rise.

Specifically, the coefficients of thermal expansion of the firstcompression coil spring 53 and the second compression coil spring 54 areselected such that in a case where flame moves upstream due to a vortexcore flashback and the temperatures of the atmosphere around thecompression coil springs 53 and 54 have risen to 700° C., the secondcompression coil spring 54 thermally elongates more than the firstcompression coil spring 53 does and the valve body 51 separates awayfrom the air spraying hole 39F. That is, the second compression coilspring 54 functions as the thermal elongation member that moves thevalve body 51 to the second position by thermal elongation.

As illustrated in FIG. 11, for example, when flame moves upstream due toa vortex core flashback and reaches the main nozzle 24, the valve body51 separates away from the opening 57 of the air spraying hole 39F onthe internal space 47F side by thermal elongation of the secondcompression coil spring 54.

Accordingly, the compressed air A is sprayed via the air spraying holes39F as purge air. By the compressed air A being sprayed, the vortex coreflashback returns to the downstream side.

By the vortex core flashback returning to the downstream side, thetemperatures of the atmosphere around the compression coil springs 53and 54 decline. Accordingly, the second compression coil spring 54contracts and the air spraying hole 39F is closed down by the valve body51 of the valve device 49. Consequently, the jetting of the compressedair A stops.

According to the embodiment, even in a case where abnormal combustionsuch as a vortex core flashback has occurred, the compressed air A fromthe air spraying hole 39F is sprayed onto the downstream side of themain nozzle 24. For this reason, it is possible to avoid a vortex coreflashback by lowering the distribution of fuel concentration of a vortexcore. Accordingly, it is possible to prevent the combustors from beingdamaged by heat due to a vortex core flashback.

In addition, the valve device 49 can be repeatedly used even after themain nozzle 24 is exposed to a vortex core flashback.

Although a member thermally elongating by a vortex core flashback is setas a compression coil spring in the embodiment, the member is notlimited thereto. A cylindrical member in which a plurality ofventilating holes are formed may be used instead of the compression coilspring.

In addition, although the air spraying hole 39F and the valve shaft 50of the embodiment extend along the burner axis Ab, the invention is notlimited thereto. A configuration where the air spraying hole 39F and thevalve shaft 50 extend in one direction of tilting with respect to theburner axis Ab may be adopted.

Although the embodiments of the invention have been describedhereinbefore, various modifications can be made without departing fromthe gist of the invention.

INDUSTRIAL APPLICABILITY

Even in a case where abnormal combustion such as a vortex core flashbackhas occurred, it is possible to avoid the vortex core flashback bycompressed air being sprayed onto the downstream side of the nozzle mainbody in the combustor and the gas turbine.

REFERENCE SIGNS LIST

-   -   1: gas turbine    -   2: compressor    -   3: combustor    -   4: turbine    -   13: combustion cylinder    -   14: fuel jetter    -   15: pilot burner    -   16: main burner (nozzle main body)    -   24: main nozzle (shaft body)    -   26: swirling blade    -   29: purge air flow path    -   29 a: air flow path main body    -   29 b: diameter increasing portion    -   34: main nozzle main body    -   35: tip portion    -   38: fuel spraying hole    -   39: air spraying hole    -   40: sealing member    -   41: fuel flow path    -   43: spraying hole main body    -   44: plate accommodating portion (recessed portion)    -   47: internal space    -   48: thin portion    -   49: valve device    -   50: valve shaft    -   51: valve body    -   53: first compression coil spring    -   54: second compression coil spring (thermal elongation member)    -   56: supporting member    -   58: shaft    -   A: air    -   Ab: burner axis    -   Da: axial direction    -   F: fuel    -   PM: premixed gas

What is claimed is:
 1. A combustor comprising: a nozzle main body thatincludes: a shaft body which extends along an axis and has, inside theshaft body, a purge air flow path, which extends along the axis to a tipportion of the shaft body and is configured to allow a compressed airflow, an air spraying hole formed in the tip portion of the shaft body,and a fuel flow path which is configured to allow a fuel flow, aswirling blade, which overhangs from an outer surface of the shaft bodyin a radial direction of the shaft body, wherein the radial direction isperpendicular to the axis, and which swirls a fluid flowing along theaxis from an upstream end of the shaft body to a downstream end of theshaft body along an axial direction, and a fuel spraying hole which isformed in the swirling blade, the fuel spraying hole connected to thefuel flow path and configured to inject the fuel flow; and a sealingmember that seals the air spraying hole, wherein the sealing member isformed of a metal having a melting point lower than a melting point of ametal forming the nozzle main body, wherein the tip portion of the shaftbody is formed in a tapered shape tapering off toward the downstream endof the shaft body, wherein the air spraying hole is configured toconnect the purge air flow path to the outer surface of the shaft bodyupon being opened by melting of the scaling member, and wherein the airspraying hole is angled with respect to the axis, and is configured toinject the compressed air flow toward the downstream end of the shaftbody.
 2. The combustor according to claim 1, wherein the sealing memberhas a plate shape, is formed around an opening of the air spraying holeon the outer surface of the shaft body, and is joined to a recessedportion into which the sealing member can be fitted.
 3. A gas turbinecomprising: the combustor according to claim 1; a compressor thatcompresses air and supplies the air to the combustor; and a turbine thatis driven by a combustion gas formed by combustion of fuel in thecombustor.